This invention relates to firing mechanisms for non-automatic firearms and more particularly to a firing mechanism of the above class suitable for use in a shot gun, which provides a high degree of sensitivity with regard to both the force necessary to discharge the firearm and the degree of movement of the mechanism required for such discharge, without loss of safety.
In the usual form of firing mechanism for non-automatic rifles and handguns, a trigger element is adapted to pivot about its mounting pin in response to a force applied to the trigger grip by the user of the gun. This movement of the trigger causes a corresponding movement of a sear element, which prior to firing, engages and holds a hammer in the cocked position. When the trigger is pulled, it pivots the sear out of engagement with the hammer, thereby releasing the hammer and allowing it to move by spring force against the firing pin. When the firing mechanism is in the cocked position the spring force acting on the hammer, bears against the sear which in turn bears against the trigger and since these forces hold the firing mechanism in the cocked position, it is necessary that they exceed any normally encountered random shocks or counter-forces which might cause the sear to pull out of engagement with the hammer and thereby accidentally to fire the gun.
In some contexts, it has been found desirable to modify certain of the parameters of the firing mechanism in order to increase the sensitivity of firing. Thus, in target shooting for example the competitive nature of the activity increases the need for the firearm to fire with a light touch and to "feel right". There are many factors which influence the intangible "feel" of a firearm such as weight, balance, trigger pull (i.e. the force needed to move the trigger), the distance the trigger travels prior to discharge, and others. Some of these factors are basically fixed and an individual shooter must decide at the time of purchase of a firearm which blend of fixed parameters best fulfills his needs. Others can be adjusted.
Examples of the provision of certain types of adjustment in rifles and handguns in the prior art include variable tension springs, means for changing the position of the sear, and honing the sear. Many of these, however, have proved unsafe. Some have been used in rifles and pistols, but none has proved successful in shot guns. The reasons for this are subtle and not easily ascertained. Shot guns are comparatively light in comparison to other firearms of similar size and their firing mechanisms are generally comparatively simple in that automatic ammunition feed devices and the like are usually not employed. In addition, shot guns are primarily bird hunting firearms designed for quick aiming, ease of loading and firing in a field setting, and to give a hunter a wide "hit" area as compared with rifles. In such a context the exposure to random shocks which might cause a misfire is even greater than with other guns and gunsmith's have been opposed to "hair trigger" adjustments for shot guns for safety reasons. In some cases gunsmith's have engaged in honing the mating elements of the sear and hammer to reduce the angle therebetween. Such a practice is dangerous for two reasons. First, the honing may be too much, and second if it is not too much to begin with, it may become too much due to wear. Honing therefore is risky and should be done only with extreme care and a gun in which the sear has been honed should be used only with extreme care.
In trap shooting, however, for many years there has been a desire among shooters to be able to have not only a safe "hair trigger" when desired, but also to be able to vary trigger pull and travel, according to the users desires under different conditions. Additional objectives of such a firing mechanism are that it be simple in construction and not require significant alteration in the shot gun balance or increase the "kick" of the gun or the manufacturing cost. In addition it should be easy to use so the shooter need not waste valuable range time making adjustments, and it must be reversible allowing both greater and lesser "pull", unlike the "honing" of parts which is irreversible. In addition it must be stable in order to avoid accidental or premature discharge during storage or transport or as the shooter reacts to the lines up his shot with the flight of the "pigeon". Standard target shooting mechanisms and hitherto known adjusting means of which I am aware have been found unsatisfactory for these purposes especially in the trap shooting context.